The present invention concerns a vertically closing closure unit for an injection molding machine.
For safety reasons, vertically closing closure units of injection molding machines must have restraint devices which prevent a moveable mold mounting plate from dropping down due to gravity if a defect, for example in the rapid-action mechanism, occurs. In the state of the art they are mounted to the rapid-action devices. In particular, in the case of hydraulic rapid-action devices, the restraint devices are in the form of clamping devices which if required act directly at the rapid-action cylinders. A basic problem with such restraint devices is that, in the event of structural failure of certain components of the rapid-action device or the restraint devices—for example fracture of fixing pins—the moveable mold mounting plate nonetheless drops down. This means that such components have to be over-sized to afford a certain safety cushion. Naturally that increases the production cost for such closure units.